1. Field of the Invention
The present invention relates to heater units for vehicles particularly for motor vehicles.
2. Description of the Prior Art
An example of a prior art heater unit for a motor vehicle is shown in FIGS. 8 through 11. Referring to the figures, the heater unit generally indicated by the reference numeral 10 includes a casing 12 formed with an air inlet 14, a defroster outlet 16, a ventilator outlet 18 and a floor outlet 20. The heater unit 10 further includes a heater core 22 and an air mix door 24 disposed within the casing 12. The heater core 22 consists of a heater core main body portion 22a and a pair of tank portions 22b, 22c at the opposite ends of the heater core main body portion 22a. With the above structure, air is drawn through the inlet 14 into the casing 12. Some of the air is then transferred to the heater core 22 in accordance with the angle of orientation of the air mix door 24 which opens by swinging about a pivot shaft 24a, while the remaining air is transferred to the outlets 16, 18, 20 without passage through the heater core 22, so that the air temperature blowing out from the outlets 16, 18, 20 is controlled depending upon the amount of heated air passed through the heater core 22 and the amount of unheated air bypassing the same. Reference numeral 26 indicates an inlet pipe and 28 indicates an outlet pipe. Engine coolant is supplied through the inlet pipe 26 to the heater core 22 and is discharged therefrom through the outlet pipe 28.
In such a prior art heater unit 10 for a motor vehicle, air flow is interrupted by heater unit components as it passes through the heater core 22' such that minimal air flow occurs through the heater core main body portion 22a at a space D.sub.1 located adjacently behind the pivotal end of the air mix door 24 with respect to the direction of air flow. Thus, space D.sub.1 is termed a so-called dead space, or space of minimal air flow, because the heater core main body portion 22a cannot efficiently heat air here. Another dead space D.sub.2 tends to form at a location D.sub.2 in front of the heater core 22 with respect to the direction of air flow. For the above reason, efficient heat exchange and good use of space are not realized by the prior art heater unit 10.
Further, the heater core 22 is in many cases designed so that the tank portions 22b and 22c, at the upper and lower ends of the heater core main body 22a, project outward beyond the casing 12 resulting in that the lower tank portion 22c is likely to interfere with a duct to be attached to the floor outlet 20 while the upper tank portion 22b projects into a narrow space adjacent an instrument panel and is likely to interfere with adjacent parts.
Still further, it is necessary for the inlet and outlet pipes 26, 28 to be bent into complicated shapes and extended over a height "h" (shown in FIG. 11) for connection to the upper tank portion 22b projecting outward of the casing 12. It is desirable that the pipes 26, 28 be simpler in shape and more compact.